To form a system of equation from a word problem, we must recognize different variables to form different equations.
Let a represent the number of child tickets.
Let b represent the number of adult tickets.
We're given:
Because we're given that a and b in total is 163, we can form the following equation:
[tex]a+b=163[/tex]
We're also given that the total sales made is $1221.80. Because we know that 1a = $6.20 and 1b = $9.40, we can also form the following equation:
[tex]6.2a+9.4b=1221.8[/tex]
Here are our two equations:
[tex]a+b=163[/tex]
[tex]6.2a+9.4b=1221.8[/tex]
We can solve using the method of elimination. Multiply both sides by 6.2 in the first equation:
[tex]6.2(a+b)=6.2(163)\\6.2a+6.2b=1010.6[/tex]
Subtract this new equation from the second equation to cancel out a:
[tex]\hspace{10}6.2a+9.4b=1221.8\\- 6.2a+6.2b=1010.6\\\rule{100}{0.5}\\3.2b=211.2[/tex]
Solve for b:
[tex]b=66[/tex]
Therefore, the number of adult tickets sold is 66.
66